DESCRIPTION The objective of this application is to produce a panel of SLT-specific human monoclonal antibodies (Hu/mAbs), that can be used safely and effectively to protect children at risk of developing HUS; in particular those presenting with bloody diarrhea, confirmed infection with SLT-producing bacteria, or sibling and other contact individuals. We have firm data which show that SLT-specific antibodies when given to piglets, well after oral challenge with E. coli 0157:H7, are highly protective against development of systemic complications and death. The recent development by GenPharm International, our collaborators, of a transgenic mouse that in response to immunization produces stable human IgM- and IgG-secreting hybridomas, makes it possible to produce SLT specific human mAbs. After production at GenPharm, the Hu/mAbs will be fully characterized at the Tufts laboratory where we have extensive experience in the derivation and characterization of SLT-specific murine mAbs. A panel of the most effective neutralizing SLT-specific Hu/mAbs will then be evaluated for their prophylactic efficacy in gnotobiotic piglets orally challenged with E. coli 0157 H7. The Specific Aims of the application are: 1. production of Hu/mAbs against SLT-II and SLT-I in HuMab transgenic mice, 2. laboratory characterization of the SLT-II and SLT-I specific Hu/mAbs, and 3. evaluation of SLT specific Hu/mAbs in piglets challenged with E. coli 0157:H7, or SLT. This is a straightforward, low-risk project requiring no new technical development, with a simple hypothesis; that a panel of highly effective SLT-specific human mAbs will much improve the clinical outcome of HUS. We predict that at the end of the support period we will have a fully characterized panel of SLT-specific human mAbs ready to be tested for safety and reactogenicity in human volunteers.